如何为移动应用制作本地存储存储文件

Question

I'm building a Xamarin CrossPlatform app all of its database is in cloud api's, but I want a local storage file in mobile which stores all login credentials whenever someone is login.

Kindly help me through this!

Answer 1

If you want to just save the login credentials you should use Xamarin.Essentials Storage

First, Add the Xamarin.Essentials NuGet package to each project.

In Android

protected override void OnCreate(Bundle savedInstanceState) {
    //...
    base.OnCreate(savedInstanceState);
    Xamarin.Essentials.Platform.Init(this, savedInstanceState); // add this line to your code
    //...

To handle runtime permissions on Android, Xamarin.Essentials must receive any OnRequestPermissionsResult. Add the following code to all Activity classes:

public override void OnRequestPermissionsResult(int requestCode, string[] permissions, [GeneratedEnum] Android.Content.PM.Permission[] grantResults)
{
    Xamarin.Essentials.Platform.OnRequestPermissionsResult(requestCode, permissions, grantResults);

    base.OnRequestPermissionsResult(requestCode, permissions, grantResults);
}

And then to save:

try
{
  await SecureStorage.SetAsync("loginCredential", "loginCredentialValue");
}
catch (Exception ex)
{
  // Possible that device doesn't support secure storage on device.
}

To retrieve:

try
{
  var loginCredential = await SecureStorage.GetAsync("loginCredential");
}
catch (Exception ex)
{
  // Possible that device doesn't support secure storage on device.
}